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Various High-speed Engines.                    633

change the order of the passages, making the steam the exhaust
passages and vice versd.

The Tower spherical engine, E, and the Fielding engine, F, are
kinematically based on Hooke's joint (Fig. 475, A). In the former
two revolving bodies, a and , are hinged on opposite sides of a
central disc or ' wobbling' piston c, the hinges being at right
angles to each other. Within the hollow sphere are four divisions,
i, 2, 3, and 4, the last shewn closed. As: the bodies a and b
rotate, and the disc c wobbles, the divisions will in turn open and
close; and it follows, conversely, that when steam is admitted to
these chambers consecutively, the said movements of the disc
and bodies will be imitated, and the shaft d rotated. To effect
this, steam is admitted on one side of the supporting web <r,
passed through proper ports to the four divisions in correct order,
and exhausted on the opposite side of e. The Fielding engine
works similarly, the practical difference being that four curved
cylinders are employed, instead of quadiri-spherical chambers, corre-
sponding pistons being formed on the central disc. A larger obtuse
angle between the inclined axes probably reduces the frictional loss.

The Westinghouse engine, G, is a type of many modern high-
speed engines, two single-acting pistons forming the equivalent
of one double-acting engine, A piston valve distributes the
steam, and the alignment of piston and crank should be noticed.
The down-stroke only being of importance, the cylinder centre-
line splits the crank radius instead of the crank circle; the con-
necting-rod's angular vibration on down-stroke is therefore halved,
and a much shorter rod may be employed, securing compactness.
During the up-stroke the rod is at a bad angle, but that is of no
consequence. The Newall engine, shewn in section at H, is
exceedingly interesting, through dispensing with so many working
parts; in fact, greater simplicity with efficiency could scarcely be
conceived. There are two sets of rings on the trunk piston,
between which are slotted holes for the passage of steam. The
distribution is effected by enlarging the trunk pin or connecting-
rod end into a hollow valve, with a partition; and ports are so
arranged that steam is admitted to, or exhausted from, the back
of the trunk, at correct times, merely by the vibration of the
connecting rod. (See J>j>. 893, 966, and 1138.)